I would choose the Beach Boys or Monkees as well with a mention to the Doors. Although I like the Byrds, I still feel they were the sloppiest band I have ever heard and I really have never categorized them in with the Beatles. Buffalo Springfield falls clear into the other side of the universe in my opinion. They had a hit or two, but if you took 50 people, you would be lucky if even 1 of those people knew or recognized their catalog (I admit that I don't know it very well). I always viewed them as a 2nd rate CSN&Y and not to be harsh, but pretty much irrelevant in popular music.
I would say that the Doors were more like the American Rolling Stones.
I think the Byrds can be compared to the Beatles when we talk about innovation and diversity. Then it is true that they never rocked out, actually their sound is characterized to be clean. But here my comparison points to their influence, because as the Beatles influenced other British bands, the Byrds were a seminal act for the beginning of new Californian bands like Jefferson Airplane, Love and Buffalo Springfield.
And I understand that Buffalo Springfield is the weakest contender of my list, because they never transcended like the other mentioned bands. They certainly were influential for the development of country rock, but as you said, they are ignored by the general public. But here my comparison was done in terms of talent, as they had three very good songwriters who later continued with relatively important careers, and they were very good interpreters as well.